1. Technical Field
The present invention relates generally to apparatus for the custom fitting of golf clubs to golfers, and, more particularly to apparatus for adjusting the lie angle and the club length and measuring the corresponding address distance of golf clubs for an individual golfer.
2. Background Art
It is well-known that a large percentage of golfers play with incorrectly-fitted or ill-fitting golf clubs. Primarily, this results because a standard set of golf clubs, 1-4 woods and 2-9 irons, for example, are manufactured to specifications determined by a "standard golfer". However, since golfers vary considerably in height, arm length and stance when addressing the golf ball, even men of the same height may have different arm and torso lengths, golfers commonly select golf clubs by trying a large number of clubs to determine which "feels" the most appropriate considering their physical makeup. Further, many of the better sets of golf clubs are not uniformly graduated from one club to the next within the set thus preventing the golfer from achieving uniformity of practice.
Each golf club has three angles associated with it: open club face angle, loft angle and lie angle. The loft angle is the angle of the striking face of a golf club head relative to a vertical axis passing through the center of the golf ball and has a critical effect on the trajectory of a golf ball when hit with the club. The lie angle is the angle of the major axis of the club shaft with respect to the horizontal plane and any error in the lie angle also has a critical effect on the trajectory of the golf ball. To avoid hooking or slicing the golf ball, the club must impact the golf ball so as to impart rotation to the ball in a direction parallel to the direction of intended travel of the ball. If the golf club is not properly oriented at the instant of impact, with the proper loft angle and lie angle, the direction of the rotation imparted to the ball may not be parallel to the intended path of travel and the resulting lift will have a horizontal vector component causing the ball to fly to the left or right of the intended path of travel. Assuming that the loft angle is correct, i.e., the golf club is oriented in the proper vertical plane, any error in the lie angle results in the golf ball being impacted at an incorrect angle. The lie angle at impact, called the effective lie angle, is a function of the lie angle built into the club and the dynamic force associated with the swinging motion.
When the golf club is held by the golfer at the correct effective lie angle, the club shaft length, which is the distance to the impact point on the club face from the lowest point of contact of the golfer's hand with the golf club's grip, is related to the address distance, i.e., the distance that the golfer stands from the tee when the ball is addressed. The measured address distance is actually the sum of two separate distances. The first is the product of the club shaft length and the cosine of the effective lie angle. The second distance is a unique distance associated with an individual address stance that is added to the first distance to obtain the measured address distance. To insure that the golf club is held at the correct effective lie angle, the golfer has to be positioned at the address distance corresponding to the club length and effective lie angle. U.S. Pat. No. 4,655,457 entitled "System to Fit Golf Club to Golfer" issued to Stanley G. Thompson on Apr. 7, 1987, discloses apparatus to measure the loft angle, lie angle and proper shaft length to custom fit a golf club to a golfer. However, even if the golf club shaft is of the proper length for a golfer's height and stance, if the golfer does not consistently address the golf ball at the proper address distance, there will be an error in the lie angle resulting in an incorrectly hit ball.
It is an object of the present invention to provide an apparatus which easily and accurately measures the shaft length and the address distance corresponding to the effective lie angle to facilitate custom fitting a golf club to a golfer.
Another object of the present invention is to provide apparatus for custom fitting of a golf club to an individual golfer which is simple to construct, lightweight and portable and which requires little skill to use.
An additional object of the present invention which is not taught in any prior art, is a unique method for fitting a number of clubs from a single set of measurements which results in the golfer being able to use a consistent stance for any number of fitted clubs with different lengths and associated lie and loft angles.